John Bowlby postulated the autonomy of attachment behavior as a behavioral system, independent of sexuality and feeding (i.e., independent of a 'secondary drive', or of 'secondary reinforcement), characterized by a need for physical proximity to the mothering caregiver, a biological function, selected by evolution, as protection against predators (Cassidy, J., Shaver, P., Handbook of Attachment, 2nd Edition, 2006, p. 5).

In addition to attachment behavior, Bowlby (A Secure Base, 1988) also describes several additional, "biologically rooted" types of behavioral systems: 1) exploratory; 2) parenting (caregiving); 3) sexual; 4) fear (Cassidy, et al, 2006, from Bowlby, 1973); and 5) eating (Lichtenberg, Lachmann, and Fosshage define 7 motivational systems, 2011 - see attached book review, on Motivational Systems Theory tab)

Bowlby identifies a situationally-elicited, "...preprogrammed set of behavior patterns...", the clarity of which contrasts sharply with the vagueness of the energic hypothesis of instinct theory's "libido".

Bowlby describes behaviors that, although prepatterned genetically, are shaped by environmental stimuli, that generate lifelong developmental trajectories and repercussions; a conceptual schema that embodies observable and measurable intersubjective configurations, between caregiver and child: "... a theoretical framework for the field compatible with the framework adopted throughout modern biology and neurophysiology..."

Bowlby maintained an unprecedented research collaboration for 40 years with Mary Ainsworth, who further expounded upon the "malleable" patterns of mother-infant communication, that can inhibit or foster the infant's reliance on mother as a "secure base", for the infant's successful exploration, growth and healthy emotional development (Wallin, 2007, pp. 15-17). Consistent with Heinz Kohut, Bowlby declared the psychobiological necessity of the normal, lifelong needs for physical proximity and secure emotional attachments with others (ibid, p. 13).